1. Field of the Invention
The present invention relates to an object (a product including a machine, a manufacture, and a composition of matter) and a method (a process including a simple method and a production method). In particular, one embodiment of the present invention relates to a power storage device and a manufacturing method thereof.
2. Description of the Related Art
In recent years, power storage devices such as nonaqueous secondary batteries (e.g., lithium secondary batteries), lithium ion capacitors, and air cells have been widely used as power supplies of consumer electric devices such as information terminals typified by mobile phones and smart phones, display devices like liquid crystal televisions, and game machines.
In particular, because of higher energy density than conventional batteries such as nickel-cadmium batteries, lithium secondary batteries are essential for information society these days as rechargeable energy supply sources for electric devices such as portable information terminals (e.g., mobile phones, smart phones, and laptop computers), portable music players, and digital cameras.
For example, lithium secondary batteries which are conventional nonaqueous secondary batteries each generally include positive electrodes and negative electrodes; the positive electrodes each include a positive electrode current collector made of sheet-like aluminum or the like and a positive electrode mix which includes a positive electrode active material capable of occluding and releasing lithium ions and which is applied to both surfaces of the positive electrode current collector, and the negative electrodes each include a negative electrode current collector made of sheet-like copper or the like and a negative electrode mix which includes a negative electrode active material capable of occluding and releasing lithium ions and which is applied to both surfaces of the negative electrode current collector. These positive electrodes and negative electrodes are rolled with a separator interposed therebetween to form a rolled body, a positive electrode tab and a negative electrode tab are connected to given portions of the positive electrodes and the negative electrodes, and an organic electrolytic solution and the rolled body where these tabs are connected to the given portions of the positive electrode and the negative electrode are sealed in an exterior body with a certain shape such as a cylindrical shape, a square shape, or a coin shape.
Further, in recent years, a solid secondary battery such as the solid secondary battery disclosed in Patent Document 1 has been actively researched. Such a solid secondary battery has a structure where an inorganic solid electrolyte or an organic polymer solid electrolyte is substituted for a conventional nonaqueous electrolytic solution and does not use a liquid material. Therefore, there is no concern for liquid leakage; further, since solid electrolytes are nonflammable, the danger of ignition can be avoided. The use of solid secondary batteries in this manner can increase safety and the structural strength of batteries. Further, simplification and enlargement of housings can be achieved. Therefore, solid secondary batteries have advantages over batteries using electrolytic solutions also in mass productivity.